When I plug a mic into the jack on my powerbook I can't get any reception from it. I go into sound , change the microphone from built-in to line-in, and i get nothing. The mic isn't on mute and from what I can see I have the right settings.
I think the hardware is fine because the audio out jack works great. This happens with many different microphones, as well.
PowerPC pwoerbook, running tiger